Drafting appliance.



0.0.BLAIR. DRAF'I'ING APPLIANOB. APPLIUATIOK FILED D116. 13, 1911.

Patented Mar. 12, 1912.

UNITED STATES PATENT OFFICE.

OLIVER C. BLAIR, 0F HOUSTON, TEXAS.

DRAFTING APPLIANCE.

Application filed December 13, 1911.

To all whom it may concern:

Be it known that I, OLIVER C. BLAIR, a citizen of the United States, residing at Houston, in the county of Harris and State of TeXas, have invented new and useful Improvements in Drafting Appliances, of which the following is a specification.

This invention relates to drafting appliances and more particularly to a combined T-square and drawing board attachment.

The object of the invention is to provide a simple, inexpensive, and efficient device which may be readily attached to an ordinary drawing board and T-square so that the T-square may be firmly held in any adjusted position on the board against accidental displacement.

Further objects of this invention will appear as the following specific description is read in connection with the accompanying drawing, which forms a part of this application, and in which- Figure 1 is a perspective view. Fig. 2 is a detail section view on the line 2-2 of Fig. 1. Fig. 3 is a similar section taken on the line 3 3 of Fig. 1.

Referring more particularly to the drawing, 1 represents an ordinary drawing board and 2 the T-square whose arm 3 extends over the board and whose head 1 is adapted to abut a rail 5 secured to the board by wood screws 6. The rail 5 comprises a strip of wood 7 rabbeted, as shown at 8, upon its outer upper edge and having secured theretoby screws 9 a metal strip or plate 10, which has a width equal to the thickness of the strip 7 and whentin position, forms with the rabbet a groove. Secured to the head @i and bridging the arm 3 is a guiding bracket 11 having an ordinary thumb piece 12 and slidably mounted on the head between the bracket and the arm 3 are a pair Specification of Letters Patent.

Patented Mar. 12, 1912.

Serial No. 665,469.

of clamping arms 13 having depending ends 14 to travel in the rabbet 8 and engage the plate or strip 10. These clamping arms are connected together at their rear ends by a bridge piece 15 which extends across the arm 3 and is provided with a vertical thumb piece 16 similar to its corresponding member 12 upon the bracket 11. Each thumb piece 12 is provided with an inwardlyextending lug 17 which holds a spiral spring 18 in position between the thumb pieces. This spring normally forces the thumb pieces apart and holds the head 1 clamped against the rail. By pinching the thumb pieces together, the depending ends 14 may be released from the rail and the T-square moved up and down the board or removed therefrom. If found expedient in practice, the rail may be made entirely of one piece either of metal or wood, with the necessary groove therein for the reception of the depending ends of the clamping arms.

Vhat is claimed is A combined drawing board and T-square attachment comprising a grooved rail adapted to be secured to a drawing board, a T- square consisting of a head and an arm secured thereon, a bracket secured on said head over the arm, a pair of clamping arms sliding in the bracket between the same and opposite sides of the arm, said clamping arms having depending ends to engag the groove, a connection between said clamping arms, and a spring interposed between the connection and the bracket.

In testimony whereof I affix my signature in presence of two witnesses.

OLIVER C. BLAIR.

\Vitnesses WV. D. BOWMAN, J. K. EDMUNDSON, Jr.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

